This project is designed to cultivate, directly in cell cultures, a variety of human and other animal rotavirus strains from diverse geographical areas and populations in order to define serotypic diversity and similarity and to select and develop potential vaccine candidates. The newly established serotype 4 rotaviruses have been shown to play an etiological role in acute gastroenteritis, and its worldwide distribution was also documented. It was shown that there is no correlation between "family" classification based on RNA-RNA hybridization and serotype designation based on neutralization. Two human rotavirus isolates from other laboratories, which are said to represent new serotypes, as well as a bovine rotavirus isolate which is suspected of belonging to serotype 2 are under investigation in our laboratory.